Max Advance Vs Borderline Correction (Octane Adjustment)

[Rbelar21]

Does anyone have any insight into how sensitive the knock sensors are when it comes to Dynamic Advance (max advance) in comparison to the Borderline corrections, or is it all the same?

I guess what I am trying to find out is if it is safer to let the Max Advance push timing up rather than the octane adjustment just immediately adding the timing to the ign timing.

I currently have a 2.3 in a Ford Ranger. I find that when i have the borderline corrections set, the power is phenomenal but sometimes I am hitting knock both in cruise (i am getting saw tooth so i know its just doing the ford thing), and high load (very little, but I really would rather see nothing or stop faster). It is not enough knock to change the OAR - but it is still knock (which i think is technically my "problem"

The real question is aimed more at high load mid to high RPM where .5 to like 1.5 degrees means it keeps pulling or it flattens out (or worse knocks and loses power. Obviously the knock sensors are doing their job and I am happy with that, but i'd like to find a way to ride the line on the safer side if that makes sense.

TLDR - is there a safe way to try to get the truck to climb towards my cyl pressure limit ceiling safetly and stop or is it "hey you're riding the line it comes with the territory"? I can't help but feel setting the borderline corrections just immedately does it no matter what, and the dynamic advance might find knock safer (even if its a little slower to get there - which leads me to figuring out how recovery and fast mode work)

[Seishuku]

How much knock are you seeing in VCM Scanner, have a log to post?

The way the system works, it constantly monitors knock, so the timing is always changing to some degree (haha)... If it sees low/no knock activity, it will increase timing all the way to cylinder pressure limit if it can.

A little knock is fine, it happens and is pretty normal in high load situations, though it shouldn't really happen in cruise. Minor spark knock is ok, it's low speed pre-ignition (LSPI, or "mega knock") is the real engine killer.
Though I've noticed on newer Ford strategies that they do tend to show knock correction in those areas as well as the typical higher load areas.
If I had to guess, I'd say that Ford tune these calibrations on the safe side even for 87 octane, then they allow the knock system to just add in timing where needed and just let the engine "self tune."

[Perna00]

I know you can set the dynamic advance and retard adjustments independently so if you want them to apply changes faster or slower, they can. Same thing with the amount of advance/retard. So even if you do not use them permanently, you can always see the values at a desired RPM/load to see what the engine ?finds? as a safe/max advance (as long as limiter are high enough) to use as a baseline. I?m almost done with an E-85 conversion and I?m going to really have to do some testing to find mine. I wonder if the dynamic advance stays in memory when the engine is cycled off/on?? If so (in theory), the engine could completely dial in max numbers for all map points on its own.

[Rbelar21]

Is there a table that it stores those "best case" values? even if it went away after key cycle? I thought it just did what you told it to and the only modifier technically is the OAR.

[Seishuku]

As far as I know, knock adjust spark advance is stored in KAM (keep alive memory), just like OAR and LTFT.
And like LTFT, I'm fairly sure it's stored as a rough table for the areas that incur the timing adjustment.

It's too bad there's no way to view or even make changes to what's store in KAM.

[Perna00]

The modifier will definitely try to add timing up to your max limits you set as long as it does not detect any knock. I know the OAR does adjust the timing separate. I’m thinking the dynamic modifier probably does not save the adjusted tables because of all changing conditions between key starts. If it did, we probably would not even have to adjust any timing except for a top advance limit because it would always do it for us.

[Perna00]

As far as I know, knock adjust spark advance is stored in KAM (keep alive memory), just like OAR and LTFT.
And like LTFT, I'm fairly sure it's stored as a rough table for the areas that incur the timing adjustment.

It's too bad there's no way to view or even make changes to what's store in KAM.

If it did, that would be a great tool to access to be able to find max limits before knock at all loads. I wonder if there is a way to document or check the saved settings.

[Rbelar21]

Can anyone explain the recovery rate tables?

Do they also impact how knock is registered / held?

[Perna00]

From my understanding, the recovery rate tables are the speed and amount of timing that it adjusts back to your desired values after it advances/pulls timing based to knock conditions.

It should not change how knock is “registered” and I don’t believe it adjusts any timing values in the memory (KAM) but I’m sure someone will correct me if I’m mistaken.

[Rbelar21]

Yeah - updating the recovery rate defintely made the dynamic timing run up quicker and i can see knock is still registered. I wonder if anyone has any insight on how detrimental this can be or if the system adds timing to quickly after a knock event that it could become a problem.

I would assume that multiple knock events will still show and are obviously bad - but this ECU sure is an interesting one.

[Perna00]

Although adjusting the dynamic advance could get you to where your max performance is going to start creating knock, you will always be better off at a stable rate that doesn’t keep getting knock retard and bumping power back down. If you have it set to always go above until it finds knock, that’s going to create quite a bit more knock occurrences versus standard driving, and I’m sure it will eventually be detrimental to the engine. An actual mileage or time frame… I’m not exactly sure. If it did not cause some damage, they would probably just use that logic versus having different timing tables for max performance.

[Rbelar21]

Agreed, I have it down lower to begin with because surprisingly the stock map actually would constantly hit knock and come back down. then go up and hit it again. I am on team any knock is bad.